The Getty Conservation Institute Solvent Gels for the Cleaning of Works of Art The Residue Question Dusan Stulik, David Miller, Herant Khanjian, Narayan Khandekar, Richard Wolbers, Janice Carlson, and W. Christian Petersen Edited by Valerie Dorge 2004 The Getty Conservation Institute Timothy P. Whalen, Director Jeanne Marie Teutónico, Associate Director, Field Projects and Science The Getty Conservation Institute works internationally to advance conservation and to enhance and encourage the preservation and understanding of the visual arts in all of their dimensions—objects, collections, architecture, and sites. The Institute serves the conservation community through scientific research; education and training; field projects; and the dissemination of the results of both its work and the work of others in the field. In all its endeavors, the Institute is committed to addressing unanswered questions and promoting the highest possible standards of conservation practice. Research in Conservation The Research in Conservation reference series presents the findings of research con­ ducted by the Getty Conservation Institute and its individual and institutional research partners, as well as state-of-the-art reviews of conservation literature. Each volume covers a topic of current interest to conservators and conservation scientists. Other volumes in the Research in Conservation series include Effects of Light on Materials in Collections (Schaeffer 2001), Bio deterioration of Stone in Tropical Environments: An Overview (Kumar and Kumar 1999), and Inert Gases in the Control of Museum Insect Pests (Selwitz and Maekawa 1998). © 2004 J. Paul Getty Trust Third printing Published by the Getty Conservation Institute, Los Angeles Getty Publications 1200 (Jetty Center Drive, Suite 500 Los Angeles, California 90049-1682 www.getty.edu/publications Patrick Pardo, Project Editor Sheila U. Berg, Copy Editor Pamela Heath, Production Coordinator Hespenheide Design, Designer Distributed in the United States and Canada by the University of Chicago Press Distributed outside the United States and Canada by Yale University Press, London Printed in the United States Library of Congress Cataloging-in-Publication Data Solvent gels for the cleaning of works of art : the residue question / Dusan Stulik ... |et al.| ; edited by Valerie Dorge. p. cm. Includes bibliographical references and index. ISBN 0-89236-759-8 (pbk.) 1. Art—Cleaning. 2. Art—Conservation and restoration. 3. Colloids. 4. Paint removers. I. Stulik, Dusan, 1956-11. Dorge, Valerie, 1946- N8560.S7 2004 702'.8'8—de22 2003025849 ISBN 978-0-89236-759-7 Illustration credits: Figure 1.1, the J. Paul Getty Museum. Plates 1 and 8, the J. Paul (Jetty Museum, © 2003 Artists Rights Society (ARS), New York/SABAM, Brussels. Figure 6.7, the J. Paul (Jetty Museum, Gift of William P. Garred. Figure. 6.1, (Jetty Conservation Institute Study Collection. Plates 2 and 9 and figures 1.2, 6.8, 6.9, and 6.10, Courtesy, Winferfhur Museum. Contents V Foreword Timothy P. Whalen vii Preface Valerie Dorge X Acknowledgments 1 Introduction Narayan Khandekar Chapter 1 5 Gelled Systems: Theory and Early Application Narayan Khandekar 5 What Is a Gel? 7 Aqueous Gel-based Cleaning Systems Chapter 2 12 Research into Potential Problems Arising from the Use of Aqueous Cleaning Systems Narayan Khandekar 12 Gel Preparation 12 Potential Problems with the Aqueous Systems Chapter 3 18 Research into Solvent Gel Residues Dusan Stulik and David Miller 18 Development of the Scientific Methodology 23 Quantitative Study of Gel Residues on Paintings 39 Quantitative Study of Gel Residues on Highly Porous and Topographically Complex Surfaces 46 Lateral Distribution of Gel Residues 54 Appendix: A Methodological Approach to Selecting a Cleaning System Richard Wolbers Chapter 4 66 Research into Solvent Residues Herant Khanjian, Dusan Stulik, and David Miller 68 Relationship between Solvent Parameters and Solvent Evaporation 68 Solvent-Paint Interaction and Evaporation 69 Quantitative Investigation of Solvent Residues 74 Results 82 Conclusions iv Contents Chapter 5 84 Aging Characteristics of Surfactants Janice Carlson and W. Christian Petersen 84 Background 86 Materials and Methods 90 Results 107 Miscellaneous Studies 109 Conclusions 111 Appendix: Interaction of MethPrep with Surfactants Chapter 6 116 Detection of Residues on the Surfaces of Museum Objects Previously Cleaned with Aqueous Gels Narayan Khandekar 116 Materials and Methods 118 Detecting Residue on a Model System 123 Examination of Museum Objects 127 Interpretation and Discussion 130 Conclusions Chapter 7 131 Project Outcome, Spin-offs, and Future Research Needs Dusan Stulik and Richard Wolters 132 Project Results 138 New Research Methodologies Resulting from the Project 138 Suggestions for Further Research into Aqueous Gel Systems and Surface Cleaning 140 A Decision Tree as a Methodological Approach to Preparing Gels for Surface Cleaning 145 References 153 Materials 156 Index 161 About the Authors Foreword I am pleased to introduce this addition to the Getty Conservation Institute's series Research in Conservation. This publication, Solvent Gels for the Cleaning of Works of Art: The Residue Question, presents the research methodologies and results of the Surface Cleaning-Gels Research Project undertaken to find answers to long-standing concerns regarding the use of aqueous cleaning methods. Aqueous cleaning methods were introduced to the conservation community in the early 1980s by Richard Wolbers of the Winterthur/ University of Delaware Program in Art Conservation as a tool for solving often complex and difficult cleaning tasks. Since that time, experience with aqueous cleaning methods has led—as is frequently the case—to questions regarding their use. Among these questions is the possible long- term effects of surface residues that remain after cleaning or layer removal using a gel formulation. Although other research institutions have undertaken studies on various aspects of aqueous cleaning systems, the residue question, partic­ ularly with regard to organic solvent-based gel formulations, remained unanswered. With the Getty Conservation Institute's commitment to addressing significant concerns in the conservation field and the imple­ mentation of its broad-based Surface Cleaning-Gels Research Project, it was fitting to focus specifically on an investigation of whether residues remain after cleaning with solvent gels, and if so, whether they might contribute to future degradation of the surface or underlying layers of works of art. The research results alleviate some of the concerns regarding residues and provide conservators with information that will allow them to make better-informed decisions in formulating a gel for a specific cleaning task. At the same time, the results of a comparative cleaning experiment using a selection of pure solvents or solvent mixtures for sur­ face cleaning support the researchers' interest in further studies on the effects of solvents on painted or varnished surfaces. The application of analytic methods used in other science fields, such as autoradiography and profilometry, during the course óf the project offers new tools for conservation research. The dedication and enthusiasm of the entire project team, Valerie Dorge, Dusan Stulik, Herant Khanjian, and former GCI colleague Narayan Khandekar, as well as colleagues in the conservation departments of the vi Foreword J. Paul Getty Museum, were instrumental to the success of the project. However, the project was a collaborative effort with a considerable num­ ber of institutions and individuals. They are acknowledged in the preface. I would like to acknowledge here the main project partners: the Depart­ ment of Chemistry, California State University, Northridge; Winterthur/ University of Delaware Program in Art Conservation; and the Conser­ vation Division of the Winterthur Museum, Garden and Library. Each institution, through its representatives—David Miller, Richard Wolbers, and Janice Carlson and W. Christian Petersen, respectively—contributed specific expertise to the various components of the project. The GCI is committed to making the results of its work available to the cultural community. The project team has made presentations to gatherings of conservation professionals on the results of components of the research as they were completed. This publication is a compilation of all the research component methodologies, data, and results. We hope that conservators will find it informative and helpful in selecting the most appropriate cleaning tool and that it will serve as a useful reference work for conservation scientists. Timothy P. Whalen, Director The Getty Conservation Institute Preface Valerie Dorge As I write this preface, I cannot resist reflecting on the paths that led me as an individual, and the Getty Conservation Institute (GCI) as a research institution, to the GCI Surface Cleaning-Gels Research Project. My intro­ duction to the Wolbers cleaning methods was in 1988 during my leave from the Canadian Conservation Institute (CCI) to complete a one-year Mellon Fellowship in polychrome sculpture at the Detroit Institute of Arts. The head of the conservation services laboratory, Barbara Heller, had just returned from a workshop at the GCI entitled "New Methods in the Cleaning of Paintings." She was enthusiastic about the new cleaning methods, and the course binder quickly became the most sought after and copied document in the lab. I could not have imagined then that some ten years